Analyses of the shielding options for HCPB DEMO blanket

• Published in: Fusion engineering and design 2020-07, Vol.156, p.111605, Article 111605
• Main Authors: Pereslavtsev, Pavel, Cismondi, Fabio, Hernández, Francisco A.
• Format: Article
• Language: English
• Subjects: Activity; Boron carbide; Boron compounds; Boron hydrides; Computer simulation; DEMO; Metal hydrides; Pressurized water; Radiation damage; Shield; Shielding; Tritium; Tungsten carbide; Tungsten compounds; Vacuum vessel; Vessels
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2020.111605

•Shielding capabilities for HCPB and WCLL breeder blanket concepts were assessed with the MCNP code.•The MCNP geometry model used for the analyses are fully heterogeneous.•The tritium breeding capabilities were calculated to be TBR=1.20 for the HCPB and 1.10 for the WCLL DEMOs.•Several shielding options were proposed to enhance the protection of the vacuum vessel behind the HCPB blanket.•The most efficient configuration of the shield was achieved with thick block of metal hydrides or tungsten based compounds (TiH2, ZrH1.6 WC or WB).•The analyses of the steel activation in the vacuum vessel demonstrate deficiency of both concepts to achieve the low-level wastes limit. The enhancement of the HCPB DEMO blanket shielding capability is a challenging issue that assumes complex studies involving numerous neutronics analyses based on the Monte Carlo simulations with MCNP code. To this end very detailed, fully heterogeneous MCNP geometry models were developed for the latest designs of the HCPB and WCLL DEMO blankets to compare their shielding efficiency. This enables to perform rigorous calculations of the nuclear responses in the blanket structure and also in the vacuum vessel that entitles to assess the shielding capability of the blankets. The basic response, tritium breeding ratio (TBR), was computed for both DEMOs and appeared to be 1.20 and 1.10 for HCPB and WCLL DEMOs respectively. Several materials were proposed for the shielding purposes including metal hydrides, tungsten compounds, boron carbide and pressurized water. Two options for the shield arrangement in the HCPB blanket were verified: inside and outside the back supporting structure (BSS) of the blanket. The most effective options appeared to be the 18 cm thick shield block made of TiH2, ZrH1.6 and WB and placed outside the BSS that can provide the dpa accumulation in the inner wall of the vacuum vessel (VV) below the results obtained for the WCLL DEMO. Activation analyses performed for both concepts revealed the challenging problem with the activity of the VV exceeding low-level waste limit.